I do have a few. Normally the oxidized layer on top should protect the whistle. Aluminiumoxide (also used as sapphire-crystal for watches due to its scratch-resistance) is rather tough but only forms a very thin layer. However over time oxidization can also destroy the material. I don't think I own any of my whistles long enough for that to occur however. I recommend getting the Dixon DX204 if you have any doubts about the aluminium. Really great whistle but the brass makes it rather heavy. Not nearly as heavy as the low D version however .

Aluminum doesn't scratch (or dent) nearly as easily as brass. Brass might not show it as readily, but it's way softer. Aluminum doesn't oxidize/corrode any more readily than brass, either. If your sweat is basic, that will cause a problem with aluminum, but if it's acidic it will cause a problem with brass.

As for my opinion on the relative merits, I don't like that aluminum feels so light. I like the weight of brass, or a more heavy-walled aluminum like Silkstone.

I have a couple Low D aluminum whistles, an MK and a Kerry optima. They are very different despite both being made of aluminum. The Optima does scratch fairly easily. The MK is anodized and has a pretty tough finish.

I put "Neolube" and cork grease on the slide, works fine so far. Neolube is graphite powder in some sort of liquid suspension that evaporates quickly

Aluminum is a much better choice than brass for a large whistle, I think.

Put me in the camp that thinks the fipple and the column of air making the sound, not the material the tube is made from

Isn't the tuning slide on the MK brass? And you're right--making a low D from brass, at least when the material has the same thickness, is not such a good idea. That's probably why they stopped making the Tony Dixon low D trad. It's incredibly heavy (over 300 gr). It can get quite uncomfy for the thumbs after a while. However when you use thin brass like the nickel-plated Howard low D it will work. But not everbody likes the "organ-pipe"-sound of the Howard.

Interesting, never thought about the weight difference, & I have only just got a Waltons high D, so can't really comment, but it doesn't sound much different to my ears, just a slight difference to my nickel & brass, whereas my ABS has a softer, slightly quieter sound.

_________________Trying to do justice to my various musical instruments.

I have had two Impempe aluminium whistles for years. One I play, the other I don't. They both look like new.I have a low D Burke as well, but it's fairly new. I don't expect any trouble with the aluminium, and sure there are none so far.

I like the look, sound, and feel of aluminum. My aluminum whistle collection is made by Anak Whistles of Korea. They combine hardwood heads with satin aluminum bodies. They are beautiful, medium volume instruments with no clogging issues. Some people have said aluminum heads could clog easily. Some aluminum whistles are thinner and are very light, while others have more heft. Some are glossy, some have a satin finish. I prefer satin finish. Brass is heavy, too heavy for my liking beyond the high D, except for Jerry Freeman's Bb, A and G, which are light, handy, beautiful instruments. Brass takes on a a patina quickly that I like. Aluminum stays looking fresh for a long time.